1. Field of the Invention
The present invention relates to a video delivery apparatus and method.
2. Description of the Related Art
The recent digitalization of video capturing devices and the spread of broadband networks has led to an increase in demand for the real-time delivery of captured video to multiple display devices. However, when video data is delivered via unicast to each of the multiple display devices directly, the video delivery apparatus experiences concentrated access. Accordingly, multicasting techniques, which deliver data to multiple display devices simultaneously, are receiving attention.
IP multicast, in which path control and replication processes for data to be delivered are carried out at the IP (Internet Protocol) layer, is known as one scheme for implementing multicast communication. However, the kind of network infrastructure required to make IP multicast usable over a wide range has not yet become widespread. Furthermore, even in cases where IP multicast could be utilized, it would often be limited to closed networks within ISPs (Internet Service Providers).
For these reasons, application-layer multicast (ALM), in which path control and replication processes for data to be delivered are carried out at the application layer, is receiving more attention. With ALM, individual display devices perform relay processing on the data to be delivered while simultaneously performing display processing for the data to be delivered, transferring the data to be delivered through packet relay. Because the relay processing among nodes is performed through unicast, wide-range video broadcast delivery spanning across ISPs can be realized using the existing network infrastructure.
In ALM, a “logical flow of data”, shown in FIG. 1B, is applied to a “physical flow of data” through routers, as shown in FIG. 1A. The logical flow of data has a tree structure with the root node at the apex thereof, and is thus called an “ALM delivery tree”. In ALM, an application can change freely the logical network configuration by reconstructing the delivery tree.
A technique that uses ALM in the delivery of videoconference data is disclosed in US Patent Laid-Open No. 2006-029092 as a video broadcast delivery technique using ALM.
A video delivery system utilizing ALM has a property whereby display devices located on lower branches of the delivery tree experience a delayed video delivery time compared to display devices located on higher branches of the delivery tree. The reason for this is that the lower the branch, the more display devices the video must be relayed through before reaching the video delivery apparatus.
Therefore, there is a problem in that when an operator who is using a display device in a lower branch controls the video delivery apparatus so as to, for example, adjust the video parameters, the video resulting from that control cannot be immediately confirmed in the display device, resulting in poor operability.